After you configure the mailbox size restriction for a mailbox, that mailbox user can continue to send and receive messages that cause the mailbox to exceed the configured mailbox size. The configured limits are enforced after a period of time, but do not take effect immediately. Restarting the Microsoft Exchange Information Store service causes the configured limits to take effect immediately.

For more information about it, please refer to the following documents:

Mailbox Size Limits Are Not Enforced in a Reasonable Period of Time

http://technet.microsoft.com/en-us/library/bb684892.aspx

To proper assist you to troubleshoot the issue, please help collect the following information:

well whenever a send receive is done , address book is also fetched. Same kind of issue came to me and then after analysing log and doing a lot google ;) . I came to a decision that we should go to send receive settings and then define the send receive groups
and from there we should UNCHECK that box.

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